The present invention relates to a method of controlling transmission of information on programs and its apparatus which method and apparatus are used for controlling transmission of program related information required by an EPG (Electronic Program Guide) system to be displayed on a television set by way of a set-top box installed on the television-watcher side where an on-air schedule including titles, channels and times of programs scheduled to be broadcasted is viewed.
In recent years, commercial services of digital television broadcasting have been started. In the digital television broadcasting, television signals of a plurality of channels are converted into digital signals to be transmitted by way of a satellite such as a broadcasting satellite or a communication satellite or a CATV (cable television) network. In this case, television signals of the channels are each compressed by using a predetermined data compressing system and then multiplexed with each other. The multiplexed data stream is transmitted by way of a transponder of the satellite or the like. On the other hand, a parabola antenna installed at the home of the television watcher receives the transmitted data stream which is then demodulated and decoded by a set-top box called an IRD (Integrated Receiver/Decoder) before being displayed on a television monitor.
As the data compressing system, in general, the MP@ML (Main Profile @ Main Level) of MPEG (Moving Picture Experts Group) 2 in accordance with an international standard ISO/ITC (International Organization for Standardization/International Electrotechnical Commission) 13818 is adopted.
In such a digital television broadcasting system, television signals of a plurality of channels are converted into digital signals, compressed and multiplexed with each other before being transformed into a data stream of one transmission channel. Then, data streams of a plurality of transmission channels are transmitted in parallel by way of a plurality of transponders each installed in a satellite for one of the transmission channels. As a result, it is possible to transmit programs of a total of typically 100 transmission channels or more at the same time.
Here, the term program used in this specification means not only a program of the television broadcasting, but also means general data contained in a unit including computer program data distributed through data broadcasting.
Now, in a digital television broadcasting system involving a number of channels as described above, the total number of broadcastable programs increases considerably, making the so-called EPG system indispensable to the television watcher. The EPG system is a program navigation system which allows the television watcher to find and select a desired program. The EPG system transmits on-air schedule information such as titles of programs scheduled to be broadcasted, their channels and times along with the programs and displays the on-air schedule information on the screen of a television monitor by way of a set-top box installed on the television-watcher side as a program table. The on-air schedule information is referred to hereafter as EPG information. The television watcher operates a pointing device or the like provided on a remote controller in order to select a desired program while looking at the grid-displayed program table in the same way as the television watcher reads a program table on a printed matter such as a newspaper or a television-guide magazine. Then, the television watcher finds the desired program and, by carrying out an operation to select the desired program on the remote controller, an operation to switch to a channel through which the selected program is being broadcasted is carried out on the IRD side, causing the selected program to be displayed on the screen of the television monitor. In this case, if a program scheduled to be broadcasted in the future is selected, for example, processing to reserve the selected program is carried out instead.
In such a related art EPG system, EPG information is transmitted through an all-time fixed bandwidth and on the basis of static scheduling. EPG information of all channels for the few coming weeks is transmitted repeatedly at fixed transmission intervals. The bandwidth does not merely mean the amount of transmission in a unit time carried out by one transponder of a satellite. Instead, it implies the amount of repeated transmission which indicates how the number of times EPG information can be transmitted repeatedly in a unit time.
Here, let us consider a case in which a data stream is transmitted by way of a transponder of a satellite for example. Since the amount of transmission per unit time carried out by one transponder is fixed, an attempt made to transmit a large amount of EPG information of all channels for several weeks will take a long time if all the data is to be transmitted. In other words, the transmission interval at which the same information on a certain specific program is retransmitted becomes long. The long transmission interval means that, if the IRD installed on the receiver side fails to take in EPG information of the specific program for some reasons caused by a transmission error or the like, it takes a long time to display a normal program table by again taking in this EPG information. That is to say, the response of the IRD is slow, that is, a period between the time the power supply of the IRD is turned on and the time all data of the most recent EPG information is taken in to display a newest program schedule is long.
On the other hand, the television watcher demands a program table covering a long period that can be looked at one time. That is to say, it is desirable to have a program table that covers as long a period as possible including future programs. However, there is a trade-off relation between the desire to increase the amount of data of the EPG information to be transmitted as a program table and the desire to improve the response of the IRD. For this reason, by taking the gain resulting from the increased amount of EPG information and the loss due to a slower response of the IRD into consideration, in the past, EPG information of an appropriate period used to be transmitted at transmission intervals which are each determined by the period.
By the way, in the related art EPG system described above, EPG information is transmitted through an all-time fixed bandwidth and on the basis of static scheduling. Thus, EPG information of all programs for the period is transmitted equally for all the programs at the same transmission intervals without regard to the frequency at which the EPG information is accessed by the television watcher. That is to say, EPG information of programs that will be most likely accessed by a number of television watchers, that is, programs that are expected to have a high degree of popularity, is not necessarily transmitted with a high priority or transmitted at a high frequency. As a result, a program table is displayed on a television monitor at the same response as that of the IRD no matter which program of the EPG information the television watcher is interested in.
In order to improve the response of the IRD under such a constraint, it is necessary to control the transmission sequence of EPG information adaptively to accesses made by the television watcher. That is to say, the transmission interval of EPG information of specific programs needs to be shortened substantially in order to increase the transmission frequency. Such specific programs include a program having a high degree of popularity, a favorite program with the television watcher, a program having something to do with the fashion or a promotion program which the broadcasting service company deliberately wants the television watcher to watch.
In particular, in the case of an IRD which can not afford to reserve a sufficient amount of memory for storing EPG information because of manufacturing-cost constraints as is the case with a home set-top box, optimization of the transmission interval of EPG information is an important problem affecting the interactive characteristic of the user interface in the operation to select a program. With the related art EPG system described above, the problem can not be solved.
It is an object of the present invention to provide a program-related-information transmission control method of controlling transmission of information on programs and an apparatus adopting the method which are capable of implementing transmission control with a predicted access trend of the television watcher taken into consideration through control of conditions for transmitting the information on programs based on past records of popularity of programs with television watchers.
To achieve the above object, according to one aspect of the present invention, there is provided a program-related-information transmission control method adopted on a data distributing side for transmitting program related information for programs to be broadcasted to a data receiving side by way of a data-transmission means, the method including the steps of: gathering information on television-watching records obtained in accordance with relevant television-watching operations from the data receiving side; and controlling conditions for transmitting the program related information of the programs on the basis of the information on television-watching records.
According to a second aspect of the present invention, there is provided a program-related-information transmission control apparatus employed on a data distributing side for transmitting program related information for programs to be broadcasted to a data receiving side by way of a data-transmission means, the apparatus including: a television-watching-record-information collecting means for gathering information on television-watching records obtained in accordance with relevant television-watching operations from the data receiving side; and a transmission-condition controlling means for controlling conditions for transmitting the program related information of programs on the basis of the information on television-watching records.
According to the configuration described above, transmission of information on programs is controlled according to dynamic scheduling with a bandwidth varying dependently upon popularity records. Thus, information on a program that will most likely be accessed by a number of television watchers is transmitted at a high frequency. As a result, the over-all access response seen by the television watcher can be improved even if the information on such a program is transmitted by way of a transmission channel having a fixed transmission capacity.